A 45 year-old man is brought to the ER with severe back pain after a RTA. Physical Examination reveals weakness, hyperreflexia, positive right Babinski sign, and loss of tactile, vibratory, and proprioceptive senses at right lower limb. The entire left lower limb has a loss of pain and temperature sensation with intact motor function. Transection of which tract resulted in the left lower extremity sensory abnormalities?